Japanese researchers have reported the use of EPR to estimate shelf life of beer. This experiment duplicated the basic experiment of those authors as a prelude to the purchase of an EPR instrument. PBN was added to aged and fresh beer and incubated at 60 degrees C; EPR measurements were performed over 3 hours. The EPR spectrum shows a lag period of up to 1 hour for fresh beer. Aged beer will have a shorter lag period. The intensity of the signal begins to rise sharply with time after the lag period.